Eczema is a term for a group of medical conditions that cause the skin to become inflamed or irritated. The most common type of eczema is known as atopic dermatitis, or atopic eczema. Atopic refers to a group of diseases with an often inherited tendency to develop other allergic conditions, such as asthma and hay fever.

Eczema affects about 10% to 20% of infants and about 3% of adults and children in the U.S. Most infants who develop the condition outgrow it by their tenth birthday, while some people continue to have symptoms on and off throughout life. With proper treatment, the disease often can be controlled.

No matter which part of the skin is affected, eczema is almost always itchy. Sometimes the itching will start before the rash appears, but when it does, the rash most commonly appears on the face, back of the knees, wrists, hands, or feet. It may also affect other areas as well.

Affected areas usually appear very dry, thickened, or scaly. In fair-skinned people, these areas may initially appear reddish and then turn brown. Among darker-skinned people, eczema can affect pigmentation, making the affected area lighter or darker.

In infants, the itchy rash can produce an oozing, crusting condition that happens mainly on the face and scalp, but patches may appear anywhere.

The exact cause of eczema is unknown, but it's thought to be linked to an overactive response by the body's immune system to an irritant. It is this response that causes the symptoms of eczema.

In addition, eczema is commonly found in families with a history of other allergies or asthma. Also, defects in the skin barrier could allow moisture out and germs in.

Some people may have "flare-ups" of the itchy rash in response to certain substances or conditions. For some, coming into contact with rough or coarse materials may cause the skin to become itchy. For others, feeling too hot or too cold, exposure to certain household products like soap or detergent, or coming into contact with animal dander may cause an outbreak. Upper respiratory infections or colds may also be triggers. Stress may cause the condition to worsen.

Although there is no cure, most people can effectively manage their disease with medical treatment and by avoiding irritants. The condition is not contagious and can't be spread from person to person.

Excerpt from:
Eczema and Your Skin | Eczema Types, Symptoms, Causes, and ...